1. Field of the Invention
The present invention relates generally to an alumina short fiber reinforced magnesium or magnesium alloy product which does not contain reaction product detrimental to mechanical characteristics. More specifically, the invention relates to a process of producing an alumina short fiber reinforced magnesium or magnesium alloy product, which does not produce reaction products detrimental to mechanical characteristics, such as fatigue characteristics, creep characteristics and so forth.
2. Description of the Background Art
Conventionally, alumina short fiber reinforced magnesium or magnesium alloy products have been produced through pressure pouring or pressure casting process. In the conventionally known process, an alumina short fiber pre-form is formed through vacuum forming process utilizing silica type or alumina type binder. The alumina short fiber pre-form is then set in a casting mold. Thereafter, molten magnesium or magnesium alloy is supplied in the casting mold. Then, pressure casting is performed by exerting pressure through a movable mold to impregnate the molten magnesium or magnesium alloy into the alumina short fiber pre-form.
In the conventional process, colloidal silica (SiO.sub.2) or colloidal alumina (Al.sub.2 O.sub.3) have been used as binders for binding the alumina short fiber for forming the pre-form. Silicon (Si) contained in the colloidal silica and aluminium (Al) contained in the colloidal alumina have a tendency to be reduced by elemental reaction during impregnation of molten magnesium or magnesium alloy. This causes increasing of concentration of Si or Al to cause segregation of Mg.sub.2 Si or Mg.sub.17 Al.sub.12. Such segregation can particularly formed at the leading edge portion of impregnation. Such segregating reacting products are brittle to cause breakage at the initial stage of plastic deformation and degrade mechanical characteristics, such as fatigue characteristics, creep characteristics of the alumina short fiber reinforced magnesium or magnesium alloy products.